During the production of natural gas by the deposits, a “coproduction” of water or of liquid hydrocarbons can also occur. At the beginning of the operation of the deposit, the flow rate of gas produced is generally high enough to naturally drive these liquids to the surface under the effect of the induced aerodynamic efforts.
When production decreases, the drop in the speed of the flow of the gas results in an increase in the pressure at the bottom of the well due to the increasing influence of the liquids that “bear down” increasingly on the column of gas. The presence of liquids, even if they are still driven by the gas, then substantially penalises the productivity of the gas extraction well.
Moreover, as soon as the flow rate of the gas produced decreases below a limit value, the liquids can no longer be driven by the gas. The liquids then accumulate at the bottom of the well, which leads almost irremediably to the stopping of production if an artificial lift is not implemented.
Diagrammatically, it can therefore be considered that during the operation of the deposit, the arrival of liquids at the bottom of the well, has for effect:                in a first step, to limit the flow rate of gas produced by the well,        in time, to limit the rate of recovery of the reserve of gas underground.        
A temporary solution can be to install velocity strings in order to accelerate the production speed of the gas and as such favour the extraction of the liquid from the well. These velocity strings most often include a decrease in the diameter of the extraction tubes. However, these velocity strings limit the instantaneous production capacity of the well and are only a temporary solution.
When the flow rate of gas produced by a well no longer makes it possible to drive the liquids to the surface (with or without velocity strings), the methods generally considered in order to resume production consist in implementing an artificial lift technique.
These artificial lifts require, most often, a continuous supply of energy:                either at the bottom of the well:                    pneumatic energy (techniques referred to as “Gas-Lift”), possibly supplemented by an injection of chemicals for the production of foam or emulsion (techniques referred to as “Foam-Lift”),            electrical energy (e.g. immersed electric pump),            hydraulic energy (e.g. hydraulic pumps, liquid-liquid ejector)                        or on the surface:                    pumps driven by a surface engine (reciprocating pumping: or continuous pumping): these solutions require transferring the mechanical power from the surface to the bottom of the well,            lowering of the pressure of the well head using gas compression units.                        
However, such artificial lift techniques are not free of defects.
Most often these artificial lift techniques require a subsequent supply of energy which penalises the economic profitability of the well.
In addition, the equipment required for implementing these methods can be cumbersome and can require heavy and complex maintenance.
Regardless of the solution retained, from among those mentioned hereinabove, the energy consumption required is often an obstacle for an implantation on isolated production sites.
There is as such a need to limit the outside supply of energy required to eliminate the liquids present in these wells, and this in a non-temporary way.
Document US 2004/0144545 A1 proposes to use a portion of the energy contained in the circulation of the gas in order to power a liquid pump and to evacuate the liquid present in the well to the surface using this pump. However, this recovery of energy requires the installation of gas turbines within a well: these gas turbines must then rotate quickly in order to supply enough energy. In addition, any impurity contained in the gas (or transported by the gas) can damage this turbine. These substantial rotating speeds decrease the resistance of these turbines and render them fragile and complex. In the event of problems with these gas turbines, any maintenance is then heavy and expensive. This invention improves the situation.